Ball joint

ABSTRACT

The invention relates to a ball joint, in particular for wheel suspensions of motor vehicles, having an outer more or less cylindrical housing, an inner joint element having a ball pivot bearing a ball section, and a bearing ring enclosing the ball section, such bearing ring being retained in the cylindrical housing, and having annular seals on both sides of the ends of the ball pivots, annular gaps which are indirectly or directly filled with a damping fluid being formed around the ball pivots adjacent to the ball section in order to achieve a hydraulic damping function.

[0001] The invention relates to a ball joint, in particular for wheelsuspensions of motor vehicles, as specified in the preamble of claim 1.

[0002] A ball joint such as this is disclosed in DE 42 07 602 A1, forexample. Such joints, which are rotatable about the central axis of theball and pivotable through a limited pivoting angle, are often used assuspension joints in wheel suspensions of motor vehicles. In addition totheir reliability and smoothness of operation, such ball joints areassigned a specific damping function for eliminating vibrations.

[0003] The object of the invention is to propose a generic ball jointwhich is advantageous from the viewpoint of structure and productiontechnology and which performs a specific damping function.

[0004] It is claimed for the invention that this object is attained bythe characteristics specified in claim 1. Advantageous developments ofthe invention are set forth in the other claims.

[0005] It is proposed in accordance with the invention that annular gapsfilled directly or indirectly with a damping fluid be formed around theball pivot adjacent to the ball section. The damping fluid, preferablyone of high viscosity, both ensures smooth operation of the ball jointnearly free of wear and at the same time effectively damps vibrationsaround the center of the ball within a specific frequency range, inparticular when the joint is used as journal bearing in wheelsuspensions of motor vehicles. The damping fluid may possesselectrorheologic or magnetorheologic properties.

[0006] In a structurally favorable embodiment the annular gaps may bebounded essentially by annular extensions on the bearing ring enclosingthe ball section. By preference the length of the annular gap should begreater than its width by a factor of 3 in order to ensure adequatedamping operation. In addition, the annular gaps preferably may beformed between tapering ball pivot sections and correspondinglyconfigured extensions on the bearing ring; this results in rugged pivotstructure and structurally more favorable sealing between the ball pivotends and the outer cylindrical housing of the ball joint.

[0007] An indirect layout in which annular tubes filled with dampingfluid are used in the annular gaps is proposed as an alternative todirect introduction of the damping fluid into the annular gaps. Specificdamping properties of the ball joint may also be imparted by shaping ofthe annular tubes (e.g., by use of fabric reinforcements) and byfunctional separation of lubrication of the joint (e.g., with grease)and the damping medium.

[0008] The annular tubes may be seated in prismatic guide rings of thecylindrical housing and butt against annular collars of the ball pivotsections formed in the area of the tubes. When the ball joint is free ofload this results in more or less linear contact between the ball pivotsections and the tubes, contact which does not impair smooth operationof the ball joint and also ensures a specified damping behavior.

[0009] Use of a damping fluid possessing electrorheologic ormagnetorheologic properties makes it possible to create a continuouslyvariable damping characteristic.

[0010] Such use permits configuration of a ball joint with controllabletorsion damping (driving-dependent change in the damping property) whichmay be employed, for example, to reduce vibration problems inmultiple-rod axles.

[0011] A damping fluid characterized by rheologic action presents theadvantage of rapid response behavior (damping control almost in realtime, so that damping in the area of the natural wheel frequency as wellis possible). The damping characteristic of the rheologic fluid may bemodified by means of a control device and the damping characteristic ofa ball joint controlled accordingly.

[0012] Two exemplary embodiments of the invention are described ingreater detail in what follows. The accompanying drawing, in the form ofdiagrams, shows in

[0013]FIG. 1, a longitudinal section through a ball joint for wheelsuspensions of motor vehicles with specified annular gaps filled withdamping fluid on both sides of the ball section; and

[0014]FIG. 2, another longitudinal section through a ball joint withhoses filled with a damping fluid mounted in annular gaps on both sidesof the ball section.

[0015]FIG. 1 shows a ball joint designated as 10 which consistsessentially of an outer cylindrical housing 12, an innerrotation-symmetric joint element 14 with a ball pivot 18, 20 bearing aball section 16 and a bearing ring 22 enclosing the ball section 16.

[0016] The joint element 14 has a through opening 24 by means of whichthis element may be fastened by means of a screw to a wheel carrier of awheel suspension of a motor vehicle. The cylindrical housing 12 may alsobe rigidly connected by a method not illustrated to a guide rod of thewheel suspension. The housing 12 and the joint element 14 are madeconventionally of metal, while the bearing ring 22 is made of a suitableplastic such as polymethylene oxide.

[0017] The bearing ring 22 enclosing the ball section 16 is designed tobe of two parts, with a plane of separation 22 a extending verticallyrelative to the joint central axis 26, and is kept axial in thecylindrical axis 12 both on the circumference side and both on anannular collar 28 on one side and on a screwed-in clamping ring 30 onthe other.

[0018] Annular seals 32 which seal the ball joint 10 from the exterior,but without impairing the required pivotability of the inner jointelement 14 about the ball section center point 34, are mounted betweenthe cylindrical sections of the ball pivot 18, 20 and the front ends ofthe cylindrical housing 10.

[0019] In addition, conical ball pivot sections 18 a, 20 a taperingtoward the ends of the ball pivot are formed between the cylindricalsections of the ball pivot 18, 20 and the ball section 16. Inconjunction with annular extensions 36,38 also tapering internally,these ball pivot sections form on the bearing ring 22 annular gaps 40,42having a length l and a mean width b, to which the statement l≧3bapplies.

[0020] The annular gaps 40, 42 are filled with a high-viscosityincompressible damping fluid or oil which is tightly enclosed betweenthe seals 32 inside the ball joint 10 and which simultaneously acts as alubricant.

[0021] When vibration of the ball joint 10 is excited around the ballsection center point 34, the annular gaps 40,42 narrow and widen on bothsides of the ball section 16 respectively and in the process displacethe damping fluid in the circumferential direction, this resulting inperformance of a specified damping function. The damping properties maybe determined by the configuration of the annular gaps 40, 42 and thestructure of the annular seals 32 respectively.

[0022] In order to avoid repetition, the ball joint 50 shown in FIG. 2is described only to the extent that it differs from the ball joint 10shown in FIG. 1. Functionally identical parts are provided with the samereference numbers.

[0023] The ball joint 50 in turn has a cylindrical outer housing 52, aninternal joint element 54 with a ball section 56 and adjoining ballpivot 58, 60.

[0024] The bearing ring 62 enclosing the ball section 56 is retainedaxially one on side by an annular collar 64 of the housing 52 and by ascrewed-in clamping ring 66 on the other.

[0025] Adjoining the foregoing a guide ring 68, 70 prismatic incross-section is fastened in the housing 52 (is pressed in or screwedin).

[0026] Spherical annular collars 72, 74 are formed on the ball pivots58, 60 radially opposite the guide rings 68, 70.

[0027] Fabric-reinforced elastic rubber tubes 80, 82 filled with ahigh-viscosity damping fluid are formed in the annular gaps 76, 78between the guide rings 68,70 and the ball pivots 58, 60.

[0028] The tubes 80,82 are seated to approximately half theircircumference in the prismatic guide rings 68, 70 and on the other siderest against the spherical annular collars 72, 74 of the ball pivots 58,60.

[0029] The annular gaps 76, 80, in turn, are sealed from the exterior bythe annular seals 32.

[0030] The damping properties of the ball joint 50 are determinedchiefly on the basis of the configuration of the tubes 80, 82, the guiderings 68, 70, the ball pivots 58, 60 with or without the annular collars72, 74, and, lastly, the seals 32. Lubricant and damping medium may bespecified and employed separately.

[0031] If a damping fluid possessing an electrorheologic property isused, it is necessary to use an electric insulating layer in the throughopening (24) of the joint element (14, 54). Similarly, the cylindricalhousing (12, 52) must be enclosed in an electrically insulating layer.The insulating layer may be, for example, in the form of an electricallyinsulating material (such as a plastic). This is necessary in order toprevent a short circuit when electric control voltage is applied to theelectrorheologic fluid. The electric control voltage is provided by acontrol device.

[0032] The electric insulating layer may be dispensed with when amagnetorheologic fluid is used. A magnetic field which permits controlof the damping characteristic of the ball joint is generated in thecavities through which damping fluid flows, by way of an external powersupply applied to an electric coil in the joint element (14, 54) or inthe cylindrical housing (12,52).

1. A ball joint, in particular for wheel suspensions of motor vehicles,having an outer more or less cylindrical housing, an inner joint elementhaving a ball pivot bearing a ball section and a bearing ring enclosingthe ball section which is retained in the cylindrical housing, andannular seals on both ends of the ball pivot, characterized in thatthere are formed around the ball pivot (18, 20), adjacent to the ballsection (16), annular gaps (40, 42) which are directly or indirectlyfilled with a damping fluid.
 2. The ball joint as claimed in claim 1,wherein the annular gaps (40, 42) are bounded essentially by annularextensions (36, 38) on the bearing ring (22).
 3. The ball joint asclaimed in claim 1 or 2, wherein the annular gaps (40, 42) as seen incross-section have a length (l) at least threefold the mean width (b) ofsuch annular gaps (l≦3 b).
 4. The ball joint as claimed in claims 1 to3, wherein the ball pivot sections (18 a, 20 a) delimiting the annulargaps (40, 42) and the extensions (36, 38) are conical in form, withdiameters decreasing in the direction of the ends of the ball pivot. 5.The ball joint as claimed in one or more of the preceding claims,wherein annular tubes (80, 82) filled with damping fluid are mounted inthe annular gaps (76, 78).
 6. The ball joint as claimed in claim 5,wherein the annular tubes (80, 82) are retained in guide rings (68, 70)prismatic in cross-section of the cylindrical housing (52).
 7. The balljoint as claimed in claim 5 or 6, wherein annular collars (72, 74)spherical in shape are formed on the ball pivots (58,60) in the area ofthe tubes (80, 82).
 8. The ball joint as claimed in one or more of thepreceding claims, wherein the damping fluid possesses electrorheologicproperties.
 9. The ball joint as claimed in claim 8, wherein an electricfield is formed, on the joint element (15, 54) and the cylindricalhousing (12, 52), in the cavities through which the damping fluid flows,by way of a control device having an external power supply, whichelectric field permits control of the damping characteristic of the balljoint.
 10. The ball joint as claimed in claims 8 and 9, wherein aninsulating ring of an electrically insulating material (such as aplastic) is introduced into the through opening (24) of the jointelement (14, 54) and wherein the cylindrical housing (12, 52) isenclosed in an electrically insulating ring in order to prevent voltageequalizing by way of an electric short circuit.
 11. The ball joint asclaimed in one or more of the preceding claims 1 to 7, wherein thedamping fluid possesses magnetorheologic properties.
 12. The ball jointas claimed in claim 11, wherein a magnetic field is formed by way of anexternal power supply on an electric coil in the joint element (15, 54)or in the cylindrical housing (12, 52), in the cavities through whichthe damping fluid flows, which magnetic field permits control of thedamping characteristic of the ball joint.